Self-sealing gasoline tank



July 9, 1946. H. P. WAGNER SELF-SEALING GASOLINE TANK NSB WSR@ unusual circumstances, is perfect.

Patented July 9, 1946 i UNITED 'sTArEs, PATE e 2,403,836v j Y sELF-SALING ansoLmTANK "Hans P. Wagner, Atlanta, Ga.

-ApplikationJune1o,1941,semaine.397,455V sclaim'si (Crim-ias) Y.

- l This invention relates to self-sealing gasoline tanks; and it comprises a tank covered with kat least one layer of plastic material comprising a water-soluble, synthetic resin insoluble in gaso- 1ine,. a 10W-freezing vehicle and a long-bered material dispersed therein in such proportions as to produce a composition remaining slightly plastic at temperatures as low as about 40 below zero Fahrenheit and having a softening or pour point at about a temperature of about 150 F.; said coatingbeing advantageously in three. layers, the outer two of which have substantially the properties stated while the intermediate layer has a composition comprising a water-soluble synthetic resin, amanti-freeze and a long-beredmaterial dispersed'there in such proportions `as to pro-Y duce a composition with a solidifying point not above about .-60 F. and a pour point not below about 100 F., said layers being advantageously enclosed by means of a wire screen and a leather or other ilexible outer covering; all as more fully hereinafter set forth and as claimed. Y

The recently-developed leak-proof or self-sealing gasoline tanks employed in fighting aeroplanes and the like are usually constructed with two layers of artificial rubber and an intermediate layer of sponge rubber. Upon puncture of the tank, the sponge rubber is adapted to swelLowing to contact with the leaking gasoline,` and this swelling in time produces stoppage of the leak.

' Under even the best of circumstances these tanks permit a considerable leakage of gasoline 'and consequently the specications for leak-proof tanks have of necessity been drawn to permit such leakage. n

It has now been found that self-sealing gasoline tanks can be constructed with plastic outer layers which, upon puncture, will quickly sealthe leak and thereaftersubstantially prevent all leakage. The Vsealing function, in all but extremely The advan# tagesy of this new construction, in comparison with the self-sealing gasoline tanks now in use, are tremendous. v n.

In thenew construction a fuel tank of synthetic rubber, metal or other material is covered with one or more of the self-sealing layers. It is advantageous to employ more than one selfsealingl layer for the reason that in this case layers ofsomewhat dilerent properties can be employed. For example, Vone layer especially adapted for'low temperature operation and another, especially adapted to Vfunction at higher ambienttemperatures, can be employed. '.Ifthree Y layersr areY employedytheintermediate tlayer Tcan" be ma'de'somewhat Ymore plastic than the 'outer' layers in order that it may function satisfactorily even at the lowest temperatures, u nderv which conditions theother layers might prove tobe too viscous Yto produce the sealing action within the desired short time interval. Such anintermedif ate layermay prove somewhat too' fluid to vfunction' satisfactorilyat the highestL summer teme, peratures, but the outer, more viscousI layers are then in -best condition, to ffunctionfsatisfactorily.

If a singler. self-sealing layer is. to ;be j used, this must of necessity be-made ;of'. intermediate properties and, While such a flayerris completeli7 satisfactory at moderate temperaturearit would befound not quite as'satisfactoryY at eitherv the highest or the lowest temperatures. The-,ideal self-sealing layer to employ would, ofcourse,`

one which would not change-in' viscosity Yfrom l the "highest summer temperatures toy the`v lower temperatures encountered in winter. The matea rialsrequiredto producei such an ideal layer are obviouslvnot Vavailable` but. materials approachf lngthisideal as closely as possible shouldbeused. l It has been found that any of the Water-soluble synthetic resins which* are insoluble in gasoline are suitable for use in thexself-sealing layersof this invention. These materials are also lknown as Aqua ResinsA and are..highly viscous vsubstances which are readily soluble ink water` and miscible Vwith'low.moleculariglycols, glycol ethers,

etc. Thesematerials are preferably mixed with a gasoline insoluble anti-freeze, such as ethylene glycol, diethylene glycol,zllssolinek glycol i (CHLCHorLCHZQinV v methyl kCellosolve (CH2OH.CH2OCH3) butyl Cellosolve (CH2OH. CH2OC4Hs),1etcL, to form alow-freezing vehicle in which to suspend a longflbered' jrnaterial, such; as asbestos or ycotton fibers' yIt is alsov advantageous toy include a small amountpf light-'weight `metallic powder asY ller,A such as magnesium or aluminumVV powders. AThe proportions of theseingredients used'are suchy as to. produce a 'plastic materialwhich has a melting or pour' pointfwhich'is abovethe highest terne peratures met in `practice and also ,al freezing'or solidifying Dorint which yis belowthevr lowest tem-'- peratures encountered infpractice. A specic `ei;- ample of a suitable Aqua Resin?? is Glybrit'ff i. e. the boric acid ester'of diethylene glycollf4 The following specic examples representv coinpositions forming Vplastic layers whichA wefhaye 'found suitable in actual practice:A 7

'Iwfhecomposition representedbyf Example 1' has a c or'igealin'gv point ofabout 40 andla pour point oil! about 15091?. that represented byJExample2=hasa solidifying point of about 609-195 and-'a softeninglpoint oil-'about `l20 Fe, while` the composition of` Example 3 has a solidif-ying; point of;V about F.- anda softening point of about 200% F.' Within the temperature ranges f indi-V catedthese layers are l eiective in` producing self*- sealingl layers usefulrin the present invcntionialthough they are particularly effective at temperatures intermediate the indicated solidifyingand softening-temperatures. i l

Inlori'e'ernbodimentA oi this inven fon the-v three layei'srrpresented bythe above specic exampl'eslarelused in combination; the compositionof Example 1. lbeing employedadjacent` the fuel tank,"V the. composition. of ExampleZ beingused. as an" intermediatelayer-and. the composition of..v Example beingy usedxasan/ outer plasticlayer. If a singlellayeris tozbe. employed. that represented by `Ilxan'iple l will vbe foundy satisfactory, while ifftwolay'ers are to beused',l the compositionsof Examples 1 and 2 in combinationaresuitable;

. Thefa'bove` described plastic layers shouldf be provided With some type of: outer. support and this-may befaccomplished by the use of: an outer covering offresilient material, Such. as leather Onarticialrubberi, forexarnple. It! is also. advis'able. to, employ. somev type. ofV stiffenina mate,- rial, such as a wire screeningijust beneath. the resilient` outer covering..v The.y entire tank con;- struction would then consist of, the inner tank wall, the three plastic layers, inthe order named, a Wire Screen @camail-r thefollierireslierltseveres- The.v methody of applying the` plastic layers o f this ,'irvention to the fuel tankV canbevariedto suit` particular conditions` of, manufacture. One method whichhas Vbeen found satisiatQliy is' to rst apply the inner plastic layerdirecftlyto,tlieJ sewed together to make a tight joint, leaving an intermediate space for the third plastic layer. This intermediate plastic layer may then be forced between the other two plastic layers by means of a so-called gun or force pump, this composition being heated ify necessary before application. By this method the entire space between the inner and the outer plastic layers may bs iillsie A1151., alter iheniermediatenyer is introd-uned,V ,the hole throughg'which was forced may be' covered overl or sevved together.

The thickness of the three layers, applied as described above, need not exceed one inch. The centen-layenmay be made 1/2 inch in thickness and theother two of a thickness of 1A inch, for example. "A: single layer of one-half inch affords coniderahleprotection and, of course, for maximum protection, three or more layers may be ap- 'piieiiieving any suitable er allowable thickness.

Example 1 Per cent Glyborte 35 to '75 Diethylene glycol to 45 Asbestos liber 5 to 25 Magnesium powder Oto 5 Example 2 i Per Cent Asbestos 'iiber' A b 5 to'1f5 Essoline'glycol (propane1,2diol) 30 to50 Aquaresin 30 to 50, Y Aluminum powder 0 to 5 0 Example 3 n Per-cent Starch Y p ,Y l0.to30 Asbestos ber 10 to' 30 Aquaresin 10130125 Ethylene glycol 5 to 20 (.unzaflfli ;0 -,t9115i Water ,29m 50;

The mode of operation of the self-sealing layersis believed to,be selfevident from the above description. l V/henfsuch; layers; are 'puncturedg the plasticity ofi the-above.. compositions. is such thata slight flow.4 ensues. 'llheislightl heat gen,- eratedi duringthe forniationgcf: the hole assists inl this` iio-w. rlhe. composition. is. heavier. than the. gasoline iiir thee tank and hence: thetendency is. for thematerialetoilow intothe tank', rather than for. thegasoline, toilow out. Only.- aslight fioW ofthe.. plastic' material;- isusually Vrequired to fill; thei hole and therrytghe. fibrous material in the composition .prevents;any tendency.` for-blowe outs. I he selig-sealing' layers described vhave been found capableofY sealing.4 over holesas large as dinchesisquarathe leakage produced being negligible. This-isbelievedtobe a new-resultan the art.

In the accompanying drawing; thereI isshown, morder less. diagrammatically a. perspective; View of; a. gasoline .tank ,provided with; theselfrseal.- ing` layersof-fthis invention. Thiasho.wing:ispro-v vided with descriptive legendswhicnare believed Seleexnanatory; The.. carnes of; the tankY is bro ken-avremo .sh witheplasticlasers.- lhree layers are Shawmut chgmay. be 0f; they Compositions repre ntedi b vf the@haveSnecicexampca The Compas ions G fzExamples 1', 2: and; 3- may; farm, i' theinnele theintcrmediate;andthe outer;nlastealaysra; f Y Y In another spe ciic example of the invention one 01".-v more.. plastic layers ofdierentpnmposition may b. sed,- The, ccmpositcn. theselayer may be. follcwsr- 05. We t@ 2%.. 0 s laaliaeii. acid; 181%.eecgoisiechproducts 0- 2.5%1i0.-0.50 %1 Gr? lessfofmasassliinpowder; Thiscomposition will. produce aleakproof lay-er Whichaiwill .withstand temperatures; .between- 200i ab ove zero't to .609' below. zero Fahrenheit. I-if only a single' layer/isto beernployedghavingi theeabove composition, this layer should hai/ela thickness cf. about oneehalflinch, whereas', if alayerioithis compositiondstoibe usedinicombinationl With'any of the., layerslof:` Examples l to-351its thickness shouldibe approximately that oi theotherlayers; the-total fthickness of the plastic layers `amounting tofr-om about-eh to-1 inch. A single layer oi-the above composition, yhaving a tlfiicknessVoi?1/2 inch will Close larselhslss erQdeeliinagasQlie .time Izwili' be. risicslillatiri theelecveccmmsinon the zinc chloride serves as an anti-freeze liquid:

, y The freezing point of this solution is about 60 F. below zero, and the solution remains unchanged up to a temperature of 200 F. or above.

The magnesium powder in the above composi- Example 5 In making the composition of this example,V from about 5 to 10 per cent of long-fibered asbestosis added to the composition of Example 4. The asbestos fibers should be saturated with zinc chloride before mixing with the other ingredients. This layer will also withstand temperatures from 200 F. above zero to 60F. below zero.

The above two layers or one of them can be used either alone or in combination with any Lor all of the layers, the compositions for which are given in Examples 1 to 3 in order t0 produce leakproof tanks. The layer containing the asbestos is advantageously placed next to the metal or rubber tank. In one embodiment the above asbestos-containing layer was.. placed adjacent the metal or rubber tank while the layer of Example 4 was used as the outer plastic layer, while a layer having a composition correspondingto Example 2 was used in between these two layers.

While several embodiments of this invention have already been disclosed, it is evident, of

course, that modifications can be made in the specic compositions and structures described without departing from the purview of this invention. It is evident, for example, that tanks within the present invention can be constructed in any desired shape or size. It is usually preferred to construct these tanks in relatively flat shape, that Yis withV a short vertical dimension, Y

in order to reduce the head of gasoline and thereby to reduce the tendency of the gasoline to escape. It has already been mentioned that any of the Aquaresins which are insoluble in gasolinecan be used in conjunction with a miscible, anti-freeze liquid which is also insoluble in gasoline to produce the desired vehicle of this invention. Any anti-freeze liquid is suitable which has the required solubility characteristics and which also has a solidifying'point not substantially above 0 F., when mixed with from Vabout toV 75 percent of Aquaresin. "I'he fibrous material to be used maybe of any suitable type, such as asbestos, hemp, cotton and other vegetable and mineral bers. These fibers must be inert to the materials with which they are contacted and should have a length ranging from about 1 to 2 inches for best results. In exextent in strength without affecting the performance oi' my tank. Thus the concentration of zinc chloride may be reduced toabout 50 perA cent, if desired, in which case it is desirable to increase the percentage of starch in order to obtain a very viscous mixture. In place of starch, other carbohydrates which swell in water, producing viscous plastic compositions, can be employed, such as gum arabic, gum tragacanth and the like, 'or even wheat our and the nlike can Y be employed. Itis also possible to employ gas expanding agents aside from magnesium powder, such as the agents employed in making light weight concretes, for example. 'Ihese agents are not essential ingredients ofr my composition but are highly advantageous.

The wire screen and outer layer of leather,`

which have been described above, may be replaced by a specially constructed layer consisting of a rather Vfine-mesh wire screen on both sides of which are placed layers of rubber, the

rubber layers being vulcanized in situ, whereby they become bonded through the meshes of the screen. One of both sides of this assembly may Ybe covered with a cloth layer, if desired. Other modications which fall within the scope vof the following claims will be immediately evident to those skilled in this art.

What is 'claimed is:

1. A self-sealing'gasoline tank comprising a shell covered with at least one layer of plastic material having a composition comprising from about 50 to 80% of a zinc chloride solution having a concentration ranging from about 50 to Y material dispersed therein, the proportions of ample 3 the gum arabic can be replaced by any other water-soluble gum, natural or artificial, and the starch can be replaced by any other amylaceous colloidal material having similar properties of increasing the viscosity of water. A preservative, suchas Moldex (an ester of parahydroxy benzoic acid) can be added to the compositionv of Example 3 or to the other compositions, if desired.

The zinc chloride solution used in the compositions of Examples 4 and 5 can be varied to some by weight, 0.5 to 2% of glacial acetic acid and 18 to 48% of anamylaceous material.

2. A self-sealing gasoline tank comprising a. shell covered with at least one layer of plastic material having a composition comprising from about 50 to 80% of a concentrated zinc chloride solution, 0.5 to 2% of glacial acetic acid,V 18 to 48% of starch and 5 to 10% of asbestos fiber.

3. A self-sealing gasoline tank comprising a shell covered with a layer of plastic material having a composition comprising from about 50 to %V of a concentrated zinc chloride solution, 0.5 tov2% of acetic acid and 18 to 48% of a starch product, and a second layer of similar composition to which has been added from about 5 to 10%V of asbestos ber.l

4. The self-sealing gasoline tank of claim 3 in combination with a third plastic layer comprising from about 10 to 75% of a Water soluble synthetic resin insoluble in gasoline, about 10- to 50% 'of a non-flammable, anti-freeze liquid which is insoluble in gasoline and in which said resin is soluble and about 5 to 25% of a long-bered inert said ingredients being such that the composition has a solidifying. point not substantially Vabove 0 F. and a pour point not substantially below 5. A self-sealing gasoline tank comprising a shell covered with a layer of plastic material having a, composition comprising from about 50'to 80 per cent of a 70 per cent zinc chloride solution, from about 0.5 to 2 per cent of glacial acetic acid, from about 18 to 48 per cent of a colloidal starch and from about 0.25 to 0.50 per cent of magnesium powder.

" HANS P. WAGNER. 

